Search results for "Mantle"

Thin crust and exposed mantle control sulfide differentiation in slow-spreading ridge magmas

2017

Composition, crystallization conditions and genesis of sulfide-saturated parental melts of olivine-phyric rocks from Kamchatsky Mys (Kamchatka, Russi…

2020

Highlights • Parental melts of sulfide-bearing KM rocks have near primary MORB-like composition. • Crystallization of these S-saturated melts occurred in near-surface conditions. • Extensive fractionation and crustal assimilation are not the causes of S-saturation. • S content in melts can be restored by accounting for daughter sulfide globules. Abstract Sulfide liquids that immiscibly separate from silicate melts in different magmatic processes accumulate chalcophile metals and may represent important sources of the metals in Earth's crust for the formation of ore deposits. Sulfide phases commonly found in some primitive mid-ocean ridge basalts (MORB) may support the occurrence of sulfide …

Subsurface chemistry of mantles of interstellar dust grains in dark molecular cores

2010

Context. The abundances of many observed compounds in interstellar molecular clouds still lack an explanation, despite extensive research that includes both gas and solid (dust-grain surface) phase reactions. Aims. We aim to qualitatively prove the idea that a hydrogen-poor subsurface chemistry on interstellar grains is responsible for at least some of these chemical "anomalies". This chemistry develops in the icy mantles when photodissociation reactions in the mantle release free hydrogen, which escapes the mantle via diffusion. This results in serious alterations of the chemical composition of the mantle because pores in the mantle provide surfaces for reactions in the new, hydrogen-poor …

Molecular and isotopic composition of free hydrocarbon gases from Sicily, Italy

2004

[1] Chemical and isotopic data have been used as geochemical tracers for a genetic characterization of hydrocarbon gases from a total of eleven manifestations located in Eastern and Central-Southern Sicily (Italy). The molecular analysis shows that almost all the samples are enriched in methane (up to 93.2% Vol.), with the exception of four gas samples collected around Mt. Etna showing high mantle-derived CO2 content. Methane isotope signatures suggest that these are thermogenic gases or a mixture between thermogenic gases and microbial gases. Although samples from some mud volcanoes in Southern Sicily (Macalube di Aragona) show isotope signatures consistent with a mixing model between ther…

Berberido aetnensis-Crataegion laciniatae, new orophilous pre-forestal alliance of the class Rhamno-Prunetea

2011

In this paper the results of a phytosociological study carried out on some aspects of shrub vegetation of forest margins are presented, investigated in the higher belt of the Madonie Mts. (Northern-Central Sicily), referred to the order Prunetalia spinosae (Rhamno-Prunetea). Through comparison with other known coenoses in the central- southern part of the Italian Peninsula and in Sicily – especially, the associations of Berberidion vulgaris and those of Pruno-Rubion ulmifolii – a coenological and phytogeographical autonomy has been made evident and has resulted in the recognition of a new alliance, described under the name Berberido aetnensis-Crataegion laciniatae Gianguzzi et al., all. nov…

Epidemiology of Mantle Cell Lymphoma: A Population-Based Study in France

2011

Abstract Abstract 5222 Introduction: Mantle cell lymphoma (MCL) is an aggressive and rare B-cell lymphoma entity representing around 5–8% of non-Hodgkin's lymphomas in adults. To our knowledge no data is available on the epidemiology of MCL in France. We aimed to describe incidence, survival and main clinical characteristics of MCL in a French population. Methods: Patients diagnosed with MCL were identified in three administrative areas covered by an haematological malignancies registry: the Côte d'Or (from 1988 to 2008), the Basse-Normandie (from 1997 to 2006) and the Gironde (from 2002 to 2006). Main clinical features and management characteristics were collected. World age-standardised …

Ancient xenocrystic zircon in young volcanic rocks of the southern Lesser Antilles island arc

2017

Abstract The Lesser Antilles arc is one of the best global examples in which to examine the effects of the involvement of subducted sediment and crustal assimilation in the generation of arc crust. Most of the zircon recovered in our study of igneous and volcaniclastic rocks from Grenada and Carriacou (part of the Grenadines chain) is younger than 2 Ma. Within some late Paleogene to Neogene (~ 34–0.2 Ma) lavas and volcaniclastic sediments however, there are Paleozoic to Paleoarchean (~ 250–3469 Ma) xenocrysts, and Late Jurassic to Precambrian zircon (~ 158–2667 Ma) are found in beach and river sands. The trace element characteristics of zircon clearly differentiate between different types o…

Halogens in volcanic systems

2009

The transport, degassing and atmospheric release of halogens from active volcanism on Earth have been the 12 focus of increasing interest over the last few decades, and have recently been the subject of the 1st workshop 13 on “Halogens in volcanic systems and their environmental impacts” that was held in December of 2007 at 14 Yosemite Lodge in Yosemite National Park, California. As an introduction to this Chemical Geology special 15 issue, collecting contributions from many of the participants at the workshop, we review here recent 16 advances in this field, including experimental and theoretical investigations of halogen behaviour in volcanic 17 and related magmatic systems. We discuss pr…

Mantle-derived fluids discharged at the Bradanic foredeep/Apulian foreland boundary: The Maschito geothermal gas emissions (southern Italy)

2014

Abstract The mephitis of Maschito, known since historical times as Lago Fetente (Smelly Lake) -although the lake is now dry-, is located 20 km from the Mt. Vulture volcanic edifice (Southern Italy). It is placed along the same regional tectonic discontinuity where some maars are located, close to the boundary between the foredeep and the Apulian foreland. About 300 m2 of surface is lacking in flora, while dead animals are frequently found all around it. The smelly exhalations are mainly composed of CO2 (∼98%), and, in lesser amounts, of H2S, N2, CH4 and other hydrocarbons. He, Ne and Ar occur in trace amounts. The CO2 isotopic composition is in the range of that of the main active Italian v…

Os, Sr, Nd, Pb, O isotope and trace element data from the Ferrar flood basalts, antarctica: evidence for an enriched subcontinental lithospheric sour…

1996

Os, Sr, Nd, Pb and O isotopes and trace element data are reported for basaltic andesite and andesite whole rocks and, in part, for selected mineral separates from the Jurassic Ferrar flood basalt province. Radiogenic Sr (> 0.709), unradiogenic Nd (εNd= −3 to −5), and radiogenic Pb isotopes, as well as low Nb/La ratios of 0.4 – 0.6 and Nb/La ratios between 0.45 and 0.6 are found for all rocks including our most primitive sample (Mg# = 71.9). This indicates involvement of either continental crust or enriched lithospheric mantle in magma genesis. 187Re/188Os correlates strongly with 187Os/188Os, with an age of 172 ± 5 Ma, in agreement with published Arsingle bondAr data. Initial 187Os/188Os of…